What Is Intermittent Fasting and Does It Really Work? Crystal Martin - The New York Times
go to original March 4, 2022

Intermittent Fasting Guide for 2022 (Doctor Mike Hansen)

Generally, intermittent fasting is a diet strategy that involves alternating periods of eating and extended fasting (meaning no food at all or very low calorie consumption). “There’s quite a bit of debate in our research community: How much of the benefits of intermittent fasting are just due to the fact that it helps people eat less? Could you get the same benefits by just cutting your calories by the same amount?” said Courtney M. Peterson, Ph.D., an assistant professor in the Department of Nutrition Sciences at the University of Alabama at Birmingham who studies time-restricted feeding, a form of intermittent fasting.

We asked Dr. Peterson and a few other experts to help us sort out the real from the scam on intermittent fasting.

How do I try intermittent fasting?

There are four popular fasting approaches: periodic fasting, time-restricted feeding, alternate-day fasting and the 5:2 diet. Time-restricted feeding, sometimes called daily intermittent fasting, is perhaps the easiest and most popular fasting method. Daily intermittent fasters restrict eating to certain time periods each day, say 11 in the morning to 7 at night. The fasting period is usually around 12 or more hours that, helpfully, includes time spent sleeping overnight. Periodic fasting will feel most familiar: no food or drinks with calories for 24-hour periods. Another type of fast, alternate-day fasting requires severe calorie reduction every other day. Lastly, the 5:2 method was popularized by author Kate Harrison’s book “The 5:2 Diet" and requires fasting on two nonconsecutive days a week.

Is fasting an effective weight-loss method?

[Update: A new study found that a popular form of intermittent fasting called time-restricted eating produced minimal weight loss and one potential downside: muscle loss.]

If you are obese or overweight, fasting is an effective weight-loss method, if you stick to it. But it is no more effective than a diet that restricts your daily calories. We know this because there were no additional weight-loss or cardiovascular benefits of fasting two days per week, over an ordinary calorie-restriction diet, in a study of 150 obese adults over the course of 50 weeks.

But you should also consider how difficult the diet will be to stick to. In a study of 100 randomized obese and overweight adults published in 2017, the dropout rate was higher with those who were fasting, 38 percent, compared with 29 percent for calorie restrictors and 26 percent for those who kept eating as they normally did.

“Some people really struggle with having to monitor their intake and constantly record food in an app every day. So the takeaway of the study was if daily calorie restriction doesn’t work for you, maybe alternate-day fasting would be a little easier,” said Krista Varady, Ph.D., professor of nutrition at the University of Illinois at Chicago and the senior author of the study. “There’s nothing magical here. We’re tricking people into eating less food, in different ways,” she said in 2017.

There is some new evidence that shows different forms of fasting are not equal — in part because some are easier than others, but also because some forms of fasting better match our body’s natural circadian rhythm, thus lowering insulin levels, increasing fat-burning hormones and decreasing appetite.

Basically, because our metabolism has evolved to digest food during the day and rest at night, changing the timing of meals to earlier in the day may be beneficial.

In a study done in Dr. Peterson’s lab, 11 adults did time-restricted feeding (eating from 8 a.m. to 2 p.m.) and a control 12-hour eating period, for four days each. On the last day of each session, researchers measured energy expenditure and hunger hormones and found that time-restricted feeding improves the appetite hormone ghrelin and increases fat burning. “It’s shown to reduce the amount of fat in the liver, which is a risk factor for diabetes and cardiovascular disease,” said Dr. Peterson.

Bottom line: If you want to lose weight and are someone who hates counting calories, you might consider fasting, as both methods offer similar weight-loss benefits.

Read the rest at The New York Times

Related: 21 Days Without Food (Prav.com)

Related: A Potential Downside of Intermittent Fasting (The New York Times)